Search Results (6,962)

316LN stainless steel is widely used in critical nuclear fusion structural components due to its excellent mechanical properties and machinability. However, its high thermal expansion coefficient and low thermal conductivity promote welding distortion, while work hardening causes residual stress accumulation. Thermo-elastic–plastic finite element modeling (FEM) is the primary numerical method for predicting these effects. Yet, despite hardware advances, full-scale simulations—especially for thick plates with multi-pass welds—remain computationally expensive, hindering the balance between efficiency and accuracy. To address the inherent trade-off between welding efficiency and dimensional accuracy in multi-pass, multi-layer welding of thick-section components, this study employs MSC. Marc to develop a finite element model of a 15 mm thick butt-welded joint fabricated from 316LN stainless steel. Three distinct heat source models—instantaneous, enhanced moving, and moving element-set—are systematically implemented to simulate transient temperature fields, residual stress distributions, and welding deformation. All numerical predictions are rigorously validated against experimental measurements to comprehensively assess both accuracy and computational efficiency. Results indicate that: (i) the predicted molten pool geometries and characteristic thermal cycle profiles from all three models exhibit strong agreement with experimental observations; (ii) longitudinal residual stress distributions predicted by all models align closely with measured values; (iii) transverse residual stresses predicted by the moving element-set and enhanced moving heat sources agree well with experiments, whereas those from the instantaneous heat source show marked deviation; (iv) angular distortion predictions from the moving element-set heat source achieve over 90% conformity with experimental data, while the instantaneous heat source substantially underestimates angular distortion, and the enhanced moving heat source yields approximately 65% agreement; and (v) in terms of computational efficiency, the instantaneous heat source requires only ~40% of the computation time needed by the moving heat source. Full article

This study investigates the elastic anisotropy and thermodynamic properties of the L1₂-type ScAl₃ phase under extreme conditions (0–1500 K and 0–50 GPa) using first-principles calculations. The elastic constants were determined using a precise stress–strain method, with polycrystalline moduli derived via the Voigt–Reuss–Hill (VRH) approximation. A systematic analysis was conducted to characterize the elastic anisotropy of Young’s modulus, shear modulus, and Poisson’s ratio. Results demonstrate that ScAl₃ is mechanically stable and exhibits near-perfect elastic isotropy (A^U = 0.0001). Thermodynamic analysis via the quasi-harmonic Debye–Grüneisen model reveals that the phase maintains its structural integrity and significant heat resistance up to 1500 K, despite thermal softening. These findings provide theoretical insights into the physical nature of ScAl₃ intermetallics and offer quantitative guidance for the design and thermal treatment of Sc-reinforced aluminum alloys in high-temperature aerospace applications due to their superior combination of strength and toughness. Full article

This paper investigates the thermal buckling behavior of a four-edge simply supported bimodular functionally graded rectangular thin plate subjected to thermal loads. Unlike existing studies, this work introduces the bimodular effect into the thermal buckling analysis of functionally graded thin plates for the first time, accounting for the influence of tension–compression modulus on the critical temperature difference. The problem is challenging due to the complexity of materials and the nonlinearity of structural thermal buckling. For the theoretical analysis, we propose a simplified mechanical model which contains the four important assumptions: there exists a neutral plane in bending; the influence of shear stresses may be neglected; the membrane effect and bending effect are considered separately; and there are two different buckling regimes: a compression-dominated pre-buckling state and a bending-dominated post-buckling state. Three types of thermal loading cases are considered, including uniform temperature rise, linear temperature gradient through the thickness, and nonlinear temperature distribution satisfying Fourier’s law of heat conduction. Within the framework of the simplified mechanical model, the pre-buckling membrane forces, equilibrium equations, and stability equations are derived, thus obtaining a closed-form analytical expression for the critical buckling temperature difference under three different temperature rise modes. The reliability of the present analytical model is validated through comparison with finite element results. Furthermore, a detailed parametric study is conducted to reveal the influences of aspect ratio, width-to-thickness ratio of plate, bimodular indices, and gradient parameters of materials on the critical temperature difference. The results provide a theoretical basis for the thermal stability design of bimodular functionally graded plates operating in high-temperature environments. Full article

To overcome the limited high-temperature capability of silica-based fiber Bragg gratings (FBGs) and the accuracy degradation of gold-coated FBGs induced by residual stress, a temperature sensor based on a gold-coated FBG with high-temperature alloy packaging is proposed and fabricated. By introducing a high-temperature annealing pretreatment to the gold-coated fiber, residual stress is effectively relieved, enabling high-precision temperature measurement in high-temperature environments. Within the range of 20–800 °C, the annealed sensor achieves an accuracy of 0.72% F.S., a sensitivity of 9.65 pm/°C, and a linearity of 0.9997, in close agreement with theoretical predictions. After ambient vibration and high-temperature thermo-vibration tests, the maximum center wavelength shifts are 13 pm and 46 pm, corresponding to temperature variations of approximately 1.35 °C@24 °C and 4.77 °C@800 °C. These results demonstrate stable sensor performance under high-temperature testing conditions. In addition, a fitting formula applicable to different center wavelengths is proposed, significantly reducing calibration effort. The sensor features a simple structure, easy installation, and reliable performance, providing an effective solution for temperature sensing in extreme environments. Full article

Glaucoma is a complex condition with an unknown exact cause, but it involves progressive damage to the optic nerve. This damage is primarily driven by high eye pressure, poor blood flow, and oxidative stress, a process linked to cell ageing and inflammation that harms the retina. Recent research highlights that these issues stem from structural changes in the eye’s drainage system and visual pathways, which can be analysed through the lens of engineering thermodynamics. This study proposes a thermal explanation for the physiological processes linking ocular behaviour to inflammatory ion flux alterations. We develop a thermal model demonstrating that temperature increases are tied to the mechanical work necessary for maintaining water flux in the anterior ocular chamber. We show that these changes alter the membrane potential and tissue pH, resulting in elevated intraocular pressure. By clarifying the temperature–pressure effect, this research establishes a theoretical framework to study the developments of future glaucoma therapies. Full article

Urban blue-green spaces play an important role in mitigating thermal environmental stress, yet their long-term configuration and relative thermal environmental benefits remain insufficiently understood at the metropolitan scale. This study examined Beijing from 2000 to 2020 by integrating Landsat time-series imagery, land-cover data, landscape metrics, land surface temperature retrieval, Geodetector analysis, and a configuration-oriented Blue-Green Environmental Benefit Index (BGEBI). The results showed that Beijing’s blue-green spaces experienced three stages: rapid decline during 2000–2003, gradual recovery during 2004–2012, and rapid expansion during 2013–2020. Spatially, low-temperature zones were mainly concentrated in the northwestern ecological conservation areas, whereas high-temperature zones were mainly distributed in the southeastern core and plain areas. Green-space landscape indicators, especially forest-related metrics, showed stronger explanatory associations with LST spatial heterogeneity than most wetland-related indicators at the metropolitan scale. The BGEBI results indicated an overall increase in relative thermal environmental benefits from 2000 to 2020, with high-value areas mainly located in the northwestern and central-western mountainous regions and low-value areas mainly distributed in southeastern urbanized areas. These findings suggest that blue-green space planning in high-density megacities should pay greater attention to landscape configuration, spatial connectivity, and scale-sensitive management. The proposed BGEBI framework provides a relative spatial-prioritization tool for identifying areas where blue-green configuration optimization may support thermal-environment improvement. Full article

To elucidate the wear evolution and failure mechanisms of VL-type composite seals in aviation hydraulic actuators under multiple operating conditions, a two-dimensional plane-strain finite element model was developed for a VL seal consisting of a PTFE L-ring and an NBR O-ring. The model incorporated the Mooney–Rivlin hyperelastic constitutive law and the Archard wear model. The effects of O-ring compression ratio, hydraulic pressure, sliding velocity, and temperature on cumulative wear, wear rate, and contact state were systematically investigated. The results show that the compression ratio has a nonlinear influence on wear. Within 8–16%, the peak wear increases approximately linearly with compression ratio; above 16%, the peak wear reaches a plateau and a secondary wear zone appears, indicating a transition from single-contact to multi-contact sealing. Hydraulic pressure promotes wear over the range of 4–28 MPa, and at 28 MPa the opposite lip edge of the L-ring comes into contact with the cylinder wall, weakening the sealing effectiveness. Within 0.1–0.3 m/s, wear increases approximately linearly with sliding velocity. However, under high velocity and insufficient hydraulic pressure, the L-ring may undergo inversion, resulting in complete seal failure. Temperature exhibits a non-monotonic effect: material softening reduces local contact stress and wear from −55 to 80 °C, whereas excessive softening at 135 °C causes the peak wear rate to increase again. A parametric analysis scheme involving an increased L-ring height and thickness, a reduced O-ring cross-section diameter, and reserved deformation space raises the critical compression ratio for stable single-contact sealing from 16% to above 20%. These findings clarify the contact-stress/contact-area competition mechanism governing VL seal wear and provide guidance for the design of aviation hydraulic actuator seals. Full article

This study investigates the flow stress behavior of Z-shaped steel wire used in cable sealing applications, over a temperature range of 20–500 °C and a strain rate range of 10⁻⁴ to 3000 s⁻¹. The primary objective is to establish reliable constitutive data to support accurate numerical simulations in relevant engineering contexts. To this end, quasi-static tensile tests, high-temperature tensile tests, and high-strain-rate dynamic compression tests were conducted using a high–low temperature electronic universal testing machine and a split Hopkinson pressure bar system. The true stress–strain responses were obtained, and the corresponding mechanical properties were systematically analyzed. Experimental results show that at room temperature (20 °C) and within the low strain rate range (10⁻⁴–10⁻¹ s⁻¹), the flow stress is insensitive to strain rate variations. However, following yielding, the slope of the flow stress curve increases noticeably with accumulating strain, indicating deformation behavior governed predominantly by strain hardening. Under high-strain-rate conditions at room temperature (20 °C, 10² to 10³ s⁻¹), the yield stress increases with increasing strain rate, revealing a pronounced strain rate sensitivity. At elevated temperatures combined with a low strain rate (300–500 °C, 10⁻³ s⁻¹), both the yield stress and the overall flow stress decrease markedly as the temperature rises, demonstrating significant thermal softening behavior. The microstructure and fracture of Z4 steel wire were observed by SEM to systematically investigate the effects of strain rate and temperature on its microstructural characteristics, thereby revealing the micro-mechanism of the material’s flow stress. Based on these experimental observations, a Johnson–Cook constitutive model was developed for the Z-shaped steel wire used in cable sealing applications. Validation results confirm that the model accurately captures the flow stress evolution of the material under coupled temperature and strain rate conditions. Full article

Global warming-induced extreme heatwaves present a severe threat to global tomato yield and production stability. To elucidate the molecular regulatory mechanisms underlying heat stress tolerance in tomato (Solanum lycopersicum), this study utilized label-free quantitative proteomics to profile alterations in protein abundance in tomato leaves in response to heat stress. A total of 294 differentially expressed proteins (DEPs) were identified, with function enrichment in the systematic activation of core stress-responsive biological processes, including the mitogen-activated protein kinase (MAPK) signaling cascade, the endoplasmic reticulum protein processing, and glutathione metabolism. Among them, heat shock protein (HSP) family members exhibited the most significant changes, particularly two small heat shock proteins (sHSPs), designated as SlsHSP1 and SlHSP17.4. Functional validation showed that silencing either SlsHSP1 or SlHSP17.4 drastically impaired heat tolerance in tomato plants. Specifically, silenced lines displayed excessive reactive oxygen species (ROS) accumulation and reduced antioxidant enzyme activities, with SlsHSP1-silenced plants showing more severe heat-induced phenotypic damage. Subcellular localization assays further demonstrated SlsHSP1 was located in the ER and SlHSP17.4 in the nucleus. Collectively, this study unravels multiple heat defense regulatory networks in tomato, in which organelle-specific sHSPs like SlsHSP1 and SlHSP17.4 synergistically maintain protein homeostasis and cellular redox balance, conferring broad-spectrum stress resistance in plants under high-temperature stress. Full article

With the development of shipping to harsh marine environment, it is very important to understand the transient behavior of a marine diesel engine in high sea conditions. Wave-induced hull motion will lead to severe load fluctuations and air-fuel ratio imbalance. In this study, an integrated simulation platform coupled with environmental loads, hull dynamics, propeller characteristics and a high-fidelity thermodynamic engine model was constructed to explore the response characteristics of the propulsion system. The model integrates a zero-dimensional multi-zone combustion method, turbocharger dynamic characteristics and an incremental PID governor, and has been verified based on the bench test data of TBD234V12 diesel engine and the 20 m Wigley standard ship. The simulation results under the sea conditions from level 7 to 9 show that the transient load has a nonlinear amplification effect. Specifically, from sea state 7 to sea state 9, the engine load fluctuation range expands by 2.0 times, while the main peak amplitude of speed fluctuation increases by 3.7 times. Furthermore, the peak exhaust pressure rises by 1.8 times, and the exhaust temperature fluctuation amplitude broadens by 35%. Frequency domain analysis further identified the low-frequency energy concentration phenomenon in the exhaust pressure spectrum and the precursor characteristics of compressor surge. The research results quantify the deterioration law of thermodynamic stability and mechanical stress under wave disturbance, and provide an important reference for the formulation of an engine robust control strategy and fatigue life assessment under high sea conditions. Full article

Functionally graded materials (FGMs) effectively alleviate residual stress induced by physical property mismatch at dissimilar material interfaces through a graded transition in composition or structure. Among these, the matching of the coefficient of thermal expansion (CTE) is a core indicator for ensuring the service reliability of the joint. Traditional composition design relies on empirical trial-and-error, which makes it difficult to efficiently identify the optimal path in a high-dimensional composition space. This study proposes a data-driven, machine learning-assisted composition design method. Based on a high-precision dataset covering 15 elements and 747 CTE data points, six typical regression models were systematically evaluated. The results show that the random forest (RF) model achieves the best performance, with a coefficient of determination (R²) of 0.929 and a root mean square error (RMSE) of 0.658 on the test set. Using the SHapley Additive exPlanations (SHAP) method, the lattice constant (c), Young’s modulus (YM), and temperature (T) were identified as the key physical descriptors governing the thermal expansion behavior. Experimental validation shows that the CTE prediction deviation of the model for the high-performance Fe-based alloy Norem02 in the range of 20–300 °C is only 0.89%. Based on this framework, the composition of the 316L/Norem02 transition layer was successfully designed in this study. This effectively reduced the interfacial thermal expansion mismatch. Consequently, it provides a reliable theoretical basis for the rational design of dissimilar material interfaces under extreme service conditions. Full article

Heat stress (HS) is among the most economically consequential environmental challenges to global dairy production, causing progressive declines in milk yield, compositional quality, and mammary cellular integrity. The temperature–humidity index (THI) is the primary thermal load metric, with performance-impairment thresholds typically beginning at THI 68 in Holstein cattle, with severe impacts manifesting beyond THI 72; breed-specific thresholds for Jersey, Brown Swiss, and Simmental cows differ owing to their lower metabolic heat load and greater inherent thermotolerance. At the molecular level, HS activates heat shock protein networks—notably HSPA1A, HSP90B1, and HSPH1—through HSF1/HSF4 transcriptional activation, while simultaneously suppressing casein genes (CSN1S1, CSN2, CSN3), lipogenic genes (FASN, SCD, CD36), amino acid transporters (SLC7A5, SLC38A2), and mTOR-AKT-STAT5 translational machinery, collectively impairing milk biosynthetic capacity. Pro-apoptotic signaling (BAX, CASP3 upregulation; BCL2 downregulation) and mitochondrial dysfunction further compromise mammary epithelial viability. Post-transcriptional regulation through miRNA, circRNA, and lncRNA competing endogenous RNA networks, alongside epitranscriptomic m6A modifications, adds further regulatory complexity. Genome-wide association studies have identified SNPs in HSP70A1A, HSPA4, TLR4, and PRLR as thermotolerance candidates compatible with sustained milk production. Nutritional supplementation with methionine, arginine, and taurine partially restores cellular synthetic capacity. Integrating multi-trait genomic selection with Bos indicus introgression, precision cooling, and targeted nutrition offers the most viable path toward climate-resilient, high-producing dairy cattle. Full article

This study presents an experimental investigation of 3D-printed poly(lactic acid) samples (PLA) subjected to high-voltage AC stress. Although additive manufacturing is gaining importance in electrical engineering, studies on FDM-printed materials have concentrated mainly on mechanical behaviour. Their dielectric strength under oil-immersed high-voltage stress—a critical aspect for insulation applications—has not been systematically investigated. Additive manufacturing is increasingly considered for auxiliary insulating components in oil-immersed high-voltage equipment; however, process-induced voids and interlayer interfaces can intensify the local electric field and reduce dielectric strength. This work evaluates the AC breakdown strength of 3D-printed PLA specimens under oil immersion using the standard AC electrical strength test method for solid insulating materials. Two parameter sets were investigated: extrusion temperature (190–240 °C ) at a constant nozzle diameter, and nozzle diameter ($0.3$–$0.6 \mathrm{mm}$) at a constant extrusion temperature of $T_{\mathrm{e}}=200°\mathrm{C}$. Breakdown data were analysed using the standard two-parameter Weibull approach typically used in the statistical evaluation of electrical insulation breakdown strength, with the results additionally expressed in terms of the $B_{10}$, $B_{50}$, and $B_{90}$ percentiles. The experimental observations were interpreted using simplified electric-field simulations representing inter-bead and interlayer voids. The results indicate that, for a given material, there exists an optimal extrusion temperature that yields the highest electrical breakdown performance. Full article

Coral reefs in the Gulf of Eilat maintain a high diversity of ~100 stony coral species. Despite intense competition for a limited substrate, this raises fundamental questions about spatial organization and mechanisms of coexistence. This study combines deep learning species classification with spatial point-pattern analysis to quantify the frequency of intragenus versus intergenus competitive contacts among four dominant coral genera, Acropora, Favia, Platygyra, and Stylophora, across 12 standardized transects at four reef sites. The ResNet-50 convolutional neural network achieved 92.3% test accuracy for genus-level identification in field imagery of 1100 test images, enabling automated detection of 487 coral–coral competitive pairs exhibiting direct physical contact. Intragenus pairs comprised only 18.3% (89/487) of contacts, significantly below the 50% expected under spatial randomness (z = −14.0, p < 0.0001) with pair correlation functions g(r) > 1 at sub-meter scales indicating conspecific clustering. Genus-specific pair frequencies correlated strongly with relative abundance and spatial coverage (r = 1), with ecological traits explaining dominance patterns: fast-growing, competitive Acropora generated high contact rates, while stress-tolerant Favia and Platygyra prevailed through longevity and defensive competition. These findings demonstrate that intergeneric competition dominates despite local congeneric aggregation, maintaining diversity through niche partitioning rather than intransitive networks, even as coral cover declines amid rising temperatures above 0.05 °C yr⁻¹ and historical eutrophication. The deep learning workflow provides a scalable baseline for monitoring anthropogenic impacts on coral competition dynamics. Full article

Optical fiber sensors deployed in harsh industrial fields, e.g., high-temperature wet-oxygen, face severe challenges in signal attenuation and mechanical degradation. While amorphous silicon oxycarbide (a-SiOC) coatings offer a promising solution due to their adjustable thermo-mechanical properties, balancing their structural density with environmental stability remains a critical technical bottleneck. In this study, a-SiOC coatings were deposited on optical fibers using hexamethyldisilane (HMDS) and trace oxygen via radio-frequency capacitively coupled plasma-enhanced chemical vapor deposition (PECVD). A systematic investigation was conducted to determine the impact of deposition temperature (70–420 °C) on the precursor dissociation kinetics, microstructural evolution, and corrosion resistance of the coatings. An elevation in temperature promotes the elimination of organic terminal groups (–CH₃, –H) and enhances surface diffusion, driving the coating from a loose, carbon-rich “polymer-like” structure (dominated by Si–C bonds) to a dense, inorganic “silica-like” skeleton (dominated by Si–O–Si bonds). High-temperature corrosion tests in a wet-oxygen environment (500–900 °C) demonstrate that the failure mechanism is highly dependent on deposition temperature. Coatings deposited at low temperatures suffer catastrophic cracking due to pronounced oxidative shrinkage and the release of volatile species, whereas coatings deposited at 420 °C exhibit microcracking caused by severe carbon phase separation and stress concentration within the rigid inorganic network. In the present system, 350 °C is identified as the optimal deposition temperature, as it achieves the best balance of network densification and structural flexibility, while exhibiting the best mechanical performance. Full article